feat: Implement Discord app UI and settings management

- Added MainUI class for displaying voice state, status icon, and buttons.
- Introduced MainUIHandler to manage UI interactions and bridge communication.
- Created SettingsUI for displaying QR code and configuration instructions.
- Implemented SettingsUIHandler to manage settings and web server interactions.
- Developed WebHandler for handling HTTP requests for settings configuration.
- Updated AppRegistry to initialize with the new Discord app descriptor.
- Enhanced InteractionHandler to support keyboard interactions across app switches.
- Updated UIHandler to manage app switching and rendering of app icons.
- Enabled QR code support in LVGL configuration.

main/ui/apps/iotdis/descriptor.cpp

@@ -0,0 +1,11 @@
+#include "ui/apps/iotdis/descriptor.h"
+
+IotDisDescriptor::IotDisDescriptor()
+  : AppDescriptor("IotDis", std::make_unique<IotDisApp>()) { }
+
+void IotDisDescriptor::draw_icon(lv_obj_t* parent) {
+  // Draw Discord icon (call/phone symbol)
+  lv_obj_t* icon = lv_label_create(parent);
+  lv_label_set_text(icon, LV_SYMBOL_CALL);
+  lv_obj_center(icon);
+}